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Neither the name of the University nor the names of its contributors 17.\" may be used to endorse or promote products derived from this software 18.\" without specific prior written permission. 19.\" 20.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 21.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 22.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 23.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 24.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 25.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 26.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 27.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 28.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 29.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 30.\" SUCH DAMAGE. 31.\" 32.\" @(#)newfs.8 8.6 (Berkeley) 5/3/95 33.\" $FreeBSD: src/sbin/newfs/newfs.8,v 1.26.2.15 2003/05/13 12:16:08 joerg Exp $ 34.\" $DragonFly: src/sbin/newfs/newfs.8,v 1.7 2007/05/20 19:29:21 dillon Exp $ 35.\" 36.Dd November 24, 2010 37.Dt NEWFS 8 38.Os 39.Sh NAME 40.Nm newfs , 41.Nm mount_mfs 42.Nd construct a new UFS file system 43.Sh SYNOPSIS 44.Nm 45.Op Fl L Ar volname 46.Op Fl NCOU 47.Op Fl S Ar sector-size 48.Op Fl T Ar disktype 49.Op Fl a Ar maxcontig 50.Op Fl b Ar block-size 51.Op Fl c Ar cylinders 52.Op Fl d Ar rotdelay 53.Op Fl e Ar maxbpg 54.Op Fl f Ar frag-size 55.Op Fl g Ar avgfilesize 56.Op Fl h Ar avfpdir 57.Op Fl i Ar bytes 58.Op Fl k Ar skew 59.Op Fl l Ar interleave 60.Op Fl m Ar free space 61.Op Fl n Ar rotational positions 62.Op Fl o Ar optimization 63.Op Fl p Ar sectors 64.Op Fl r Ar revolutions 65.Op Fl s Ar size 66.Op Fl t Ar tracks 67.Op Fl u Ar sectors 68.Op Fl v 69.Op Fl x Ar sectors 70.Ar special 71.Nm mount_mfs 72.Op Fl NU 73.Op Fl F Ar file 74.Op Fl T Ar disktype 75.Op Fl a Ar maxcontig 76.Op Fl b Ar block-size 77.Op Fl c Ar cylinders 78.Op Fl d Ar rotdelay 79.Op Fl e Ar maxbpg 80.Op Fl f Ar frag-size 81.Op Fl i Ar bytes 82.Op Fl m Ar free space 83.Op Fl n Ar rotational positions 84.Op Fl o Ar options 85.Op Fl s Ar size 86.Op Fl v 87.Ar special node 88.Sh DESCRIPTION 89.Nm Newfs 90is used to initialize and clear filesystems before first use. 91Before running 92.Nm 93or 94.Nm mount_mfs , 95the disk must be labeled using 96.Xr disklabel 8 . 97.Nm Newfs 98builds a file system on the specified special file. 99(We often refer to the 100.Dq special file 101as the 102.Dq disk , 103although the special file need not be a physical disk. 104In fact, it need not even be special.) 105Typically the defaults are reasonable, however 106.Nm 107has numerous options to allow the defaults to be selectively overridden. 108.Pp 109.Nm Mount_mfs 110is used to build a file system in virtual memory and then mount it 111on a specified node. 112.Nm Mount_mfs 113exits and the contents of the file system are lost 114when the file system is unmounted. 115If 116.Nm mount_mfs 117is sent a signal while running, 118for example during system shutdown, 119it will attempt to unmount its 120corresponding file system. 121The parameters to 122.Nm mount_mfs 123are the same as those to 124.Nm . 125If the 126.Fl T 127flag is specified (see below), the special file is unused. 128Otherwise, it is only used to read the disk label which provides 129a set of configuration parameters for the memory based file system. 130The special file is typically that of the primary swap area, 131since that is where the file system will be backed up when 132free memory gets low and the memory supporting 133the file system has to be paged. 134.Pp 135.Nm mount_mfs 136creates the raw character device 137.Pa /dev/mfs<PID> 138to represent the backing store while the mount is active. This device may 139be read but not written and allows swap-based MFS filesystems to be dumped 140if desired. 141.Pp 142The following options define the general layout policies: 143.Bl -tag -width indent 144.It Fl T Ar disktype 145For backward compatibility and for 146.Nm mount_mfs . 147.It Fl F Ar file 148.Nm Mount_mfs 149will use this file for the image of the filesystem. When 150.Nm mount_mfs 151exits, this file will be left behind. 152.It Fl C 153Tell 154.Nm Mount_mfs 155to copy the underlying filesystem into the MFS mount being created 156over it. 157.It Fl L Ar volname 158Add a volume label to the new file system. 159.It Fl N 160Cause the file system parameters to be printed out 161without really creating the file system. 162.It Fl O 163Create a 164.Bx 4.3 165format filesystem. 166This options is primarily used to build root filesystems 167that can be understood by older boot ROMs. 168.It Fl T 169Use information for the specified disk from 170.Pa /etc/disktab 171instead of trying to get geometry information from the 172storage device. 173.It Fl U 174Enables soft updates on the new filesystem. 175.It Fl a Ar maxcontig 176Specify the maximum number of contiguous blocks that will be 177laid out before forcing a rotational delay (see the 178.Fl d 179option). 180The default value is 1. 181See 182.Xr tunefs 8 183for more details on how to set this option. 184.It Fl b Ar block-size 185The block size of the file system, in bytes. It must be a power of 2. The 186default size is 16384 bytes, and the smallest allowable size is 4096 bytes. 187The optimal block:fragment ratio is 8:1. 188Other ratios are possible, but are not recommended, 189and may produce unpredictable results. 190.It Fl c Ar #cylinders/group 191The number of cylinders per cylinder group in a file system. The default 192is to compute the maximum allowed by the other parameters. This value is 193dependent on a number of other parameters, in particular the block size 194and the number of bytes per inode. 195.It Fl d Ar rotdelay 196This parameter once specified the minimum time in milliseconds required to 197initiate another disk transfer on the same cylinder. It was used in determining 198the rotationally optimal layout for disk blocks within a file. Modern disks 199with read/write-behind achieve higher performance with this feature disabled, so 200this value should be left at the default value of 0 milliseconds. See 201.Xr tunefs 8 202for more details on how to set this option. 203.It Fl e Ar maxbpg 204Indicate the maximum number of blocks any single file can 205allocate out of a cylinder group before it is forced to begin 206allocating blocks from another cylinder group. 207The default is about one quarter of the total blocks in a cylinder group. 208See 209.Xr tunefs 8 210for more details on how to set this option. 211.It Fl f Ar frag-size 212The fragment size of the file system in bytes. It must be a power of two 213ranging in value between 214.Ar blocksize Ns /8 215and 216.Ar blocksize . 217The default is 2048 bytes. 218.It Fl g Ar avgfilesize 219The expected average file size for the file system. 220.It Fl h Ar avgfpdir 221The expected average number of files per directory on the file system. 222.It Fl i Ar number of bytes per inode 223Specify the density of inodes in the file system. 224The default is to create an inode for every 225.Pq 4 * Ar frag-size 226bytes of data space. 227If fewer inodes are desired, a larger number should be used; 228to create more inodes a smaller number should be given. 229One inode is required for each distinct file, so this value effectively 230specifies the average file size on the file system. 231.It Fl m Ar free space \&% 232The percentage of space reserved from normal users; the minimum free 233space threshold. 234The default value used is 235defined by 236.Dv MINFREE 237from 238.In ufs/ffs/fs.h , 239currently 8%. 240See 241.Xr tunefs 8 242for more details on how to set this option. 243.It Fl n Ar number of distinguished rotational positions 244.Xr UFS 5 245has the ability to keep track of the availability of blocks at different 246rotational positions, so that it could lay out the data to be picked up with 247minimum rotational latency. This parameter specifies the default number of 248rotational positions to distinguish. 249.Pp 250Nowadays this value should be set to 1 (which essentially disables the 251rotational position table) because modern drives with read-ahead and 252write-behind do better without the rotational position table. 253.It Fl o Ar optimization\ preference 254.Pq Cm space No or Cm time . 255The file system can either be instructed to try to minimize the time spent 256allocating blocks, or to try to minimize the space fragmentation on the disk. 257If the value of minfree (see above) is less than 8%, 258the default is to optimize for 259.Cm space ; 260if the value of minfree is greater than or equal to 8%, 261the default is to optimize for 262.Cm time . 263See 264.Xr tunefs 8 265for more details on how to set this option. 266.It Fl s Ar size 267The size of the file system in sectors. This value defaults to the size of the 268raw partition specified in 269.Ar special 270(in other words, 271.Nm 272will use the entire partition for the file system). 273.It Fl v 274Specify that the disk does not contain any partitions, and that 275.Nm 276should build a file system on the whole disk. 277This option is useful for synthetic disks such as 278.Nm vinum . 279It may also be used to allow 280.Nm 281to operate on regular files. 282When operating on a regular file, 283.Nm 284will synthesize a reasonable geometry for the filesystem. 285.El 286.Pp 287The following options override the standard sizes for the disk geometry. 288Their default values are taken from the disk label. 289Changing these defaults is useful only when using 290.Nm 291to build a file system whose raw image will eventually be used on a 292different type of disk than the one on which it is initially created 293(for example on a write-once disk). 294Note that changing any of these values from their defaults will make 295it impossible for 296.Xr fsck 8 297to find the alternate superblocks if the standard superblock is lost. 298.Bl -tag -width indent 299.It Fl S Ar sector-size 300The size of a sector in bytes (almost never anything but 512). 301.It Fl k Ar sector \&0 skew , per track 302Used to describe perturbations in the media format to compensate for 303a slow controller. 304Track skew is the offset of sector 0 on track N relative to sector 0 305on track N-1 on the same cylinder. 306This option is of historical importance only; modern controllers are always fast 307enough to handle operations back-to-back. 308.It Fl l Ar hardware sector interleave 309Used to describe perturbations in the media format to compensate for 310a slow controller. 311Interleave is physical sector interleave on each track, 312specified as the denominator of the ratio: 313.Dl sectors read/sectors passed over 314Thus an interleave of 1/1 implies contiguous layout, while 1/2 implies 315logical sector 0 is separated by one sector from logical sector 1. 316This option is of historical importance only; the physical sector layout of 317modern disks is not visible from outside. 318.It Fl p Ar spare sectors per track 319Spare sectors (bad sector replacements) are physical sectors that occupy 320space at the end of each track. 321They are not counted as part of the sectors/track 322.Pq Fl u 323since they are not available to the file system for data allocation. 324This option is of historical importance only. Modern disks perform their own 325bad sector allocation. 326.It Fl r Ar revolutions/minute 327The speed of the disk in revolutions per minute. This value is no longer of 328interest, since all the parameters which depend on it are usually disabled. 329.It Fl t Ar #tracks/cylinder 330The number of tracks/cylinder available for data allocation by the file 331system. 332The default is 1. 333If zero is specified, the value from the device geometry will be used. 334.It Fl u Ar sectors/track 335The number of sectors per track available for data allocation by the file 336system. 337The default is 4096. 338If zero is specified, the value from the device geometry will be used. 339This does not include sectors reserved at the end of each track for bad 340block replacement (see the 341.Fl p 342option). 343.It Fl x Ar spare sectors per cylinder 344Spare sectors (bad sector replacements) are physical sectors that occupy 345space at the end of the last track in the cylinder. 346They are deducted from the sectors/track 347.Pq Fl u 348of the last track of each cylinder since they are not available to the file 349system for data allocation. 350This option is of historical importance only. Modern disks perform their own 351bad sector allocation. 352.El 353.Pp 354The options to the 355.Nm mount_mfs 356command are as described for the 357.Nm 358command, except for the 359.Fl o 360option. 361.Pp 362That option is as follows: 363.Bl -tag -width indent 364.It Fl o 365Options are specified with a 366.Fl o 367flag followed by a comma separated string of options. 368See the 369.Xr mount 8 370man page for possible options and their meanings. 371.El 372.Sh EXAMPLES 373.Dl newfs /dev/ad3s1a 374.Pp 375Creates a new 376.Xr UFS 5 377file system on 378.Pa ad3s1a . 379.Nm 380will use a block size of 16384 bytes, a fragment size of 2048 bytes 381and the largest possible number of cylinders per group. 382These values tend to produce better performance for most applications 383than the historical defaults 384(8192 byte block size and 1024 byte fragment size). 385This large fragment size 386may lead to large amounts of wasted space 387on filesystems that contain a large number of small files. 388.Pp 389.Dl mount_mfs -s 131072 -o nosuid,nodev,nosymfollow /dev/da0s1b /tmp 390.Pp 391Mount a 64 MB large memory file system on 392.Pa /tmp , 393with 394.Xr mount 8 395options 396.Cm nosuid , 397.Cm nodev , 398and 399.Cm nosymfollow . 400.Sh SEE ALSO 401.Xr fdformat 1 , 402.Xr UFS 5 , 403.Xr disktab 5 , 404.Xr fs 5 , 405.Xr camcontrol 8 , 406.Xr disklabel 8 , 407.Xr dumpfs 8 , 408.Xr fsck 8 , 409.Xr mount 8 , 410.Xr tunefs 8 , 411.Xr vinum 8 412.Rs 413.%A M. McKusick 414.%A W. Joy 415.%A S. Leffler 416.%A R. Fabry 417.%T A Fast File System for UNIX 418.%J ACM Transactions on Computer Systems 2 419.%V 3 420.%P pp 181-197 421.%D August 1984 422.%O (reprinted in the BSD System Manager's Manual) 423.Re 424.Sh HISTORY 425The 426.Nm 427command appeared in 428.Bx 4.2 . 429